guidance.
Surveyors
walked
these
transects,
and
recordings
were
automatically taken every 0.5 metres. Where tree cover prevented GPS recordings within the prescribed tolerance levels, EDM Total Stations were set up and used to take readings. This method fits in with English Heritage suggestions for interchanging between GPS and EDM survey (Ainsworth, S. & Thomason, B. 2003). EDM survey was employed where GPS signal was not sufficient, for general topographic readings, as part of the systematic survey process.
5.1.5. Subjective survey
Subjective survey was used as a means to record features in more detail. It relies on the expertise of the surveyor to analyse the earthworks and to record them. For this procedure, EDM Total Stations were used to record the tops and bottoms of slopes. These recordings were highlighted in the survey data using the feature code facility available in total stations. This subjective survey method was employed in order to allow a hachure plan of the site to be created as recommended by English Heritage (Bowden 2006). This was then used for interpretation.
5.1.6. Data preparation and analysis.
All data was processed in Mapinfo Geographic Information Systems (GIS). Vertical Mapper 3.0: Spatial Analysis and Display software, a Mapinfo software extension was used to create a nearest neighbour interpolation model to present the site in 3D. This Digital Elevation Model (DEM) was then subject to slope surface analysis, which measures and displays relative slope severity. In order to interpret the 3-Dimensional earthworks in a 2-Dimensional map, the data has been plotted using a combination of objective contouring, and subjective hachure plans, as recommended by English Heritage. This plan produced in MapInfo and Vertical Mapper software, and was drawn to English Heritage conventions (Ainsworth, S., Bowden, M., McOmish, D. & Pearson, T. 2007. pp14-19).
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